A charge pump (also known as a Dickson charge pump or Dickson multiplier) takes a low voltage DC supply as its input, and so is a kind of low voltage DC to DC converter that uses capacitors as energy storage elements to create either a higher or lower voltage power source at the charge pump's output. In addition to the DC input, the circuit generally requires a feed of two clock pulse trains with an amplitude swinging between the DC supply rails. These pulse trains usually have opposite polarities. Charge pump circuits are capable of high efficiencies, sometimes as high as 90-95% while being electrically simple circuits. Charge pumps can provide double voltages, triple voltages, halve voltages, invert voltages, fractionally multiply or scale voltages (such as ×3/2, ×4/3, ×2/3, etc.) or generate arbitrary voltages, depending on the controller and circuit topology.
However, with constant down-scaling and increasingly demanding requirements to the speed and functionality of ultra-high density integrated circuits, the interconnection wiring between the transistors and capacitors of a charge pump circuit becomes increasingly problematic. In order for the charge pumps 40 (in FIG. 2A) and 50 (in FIG. 2B) to function, electrical continuity must be established between each transistor's source and gate, and between the clock signals and the capacitors. Additionally, electrical continuity must be established between each capacitor, the drain of one transistor and the source of an adjacent transistor. In prior art integrated circuits, these charge pump interconnections often involve a plurality of metal interconnections and contacts between capacitors and transistors that can take up space, and/or extend for relatively long distances and contacts (or vias) through several layers within the integrated circuit.
Additionally, as the technology is down-scaled, the supply voltage (typically referred to as Vdd) is also down-scaled. The lower the supply voltage, the more stages are required in a charge pump circuit to meet various voltage requirements throughout the integrated circuit. Therefore a compact design for an integrated circuit charge pump becomes an ever-more increasing premium as the technology is scaled.
Accordingly, there is a need for a charge pump circuit design, and method of making the same, that reduces the amount of metal interconnection wiring required between capacitors and transistors in a charge pump circuit. Additionally, there is a need for a more compact design for a charge pump circuit compared to prior art charge pumps.